Low leakage connector for use in high radiation fields



D. w. NOREN 3,514,741

LOW LEAKAGE CONNECTOR FOR USE IN HIGH RADIATION FIELDS May 26, 1970Filed May 3, 1968 United States Patent 3,514,741 LOW LEAKAGE CONNECTORFOR USE IN HIGH RADIATION FIELDS Don W. Noren, Redwood City, Calif.,assignor to Litton Precision Products, Inc., San Carlos, Calif., acorporation of Delaware Filed May 3, 1968, Ser. No. 726,483 Int. Cl.H01r 13/52 US. Cl. 339-60 4 Claims ABSTRACT OF THE DISCLOSURE Theimproved electrical connector means of the invention includes thestructure of conventional male and female coaxial connectors. Thatconventional structure is modified so as to avoid the existence of anyair path between the center conductor and the outer conductor of thecoaxial connector portions after the two portions are fully coupled orjoined together. One connector portion, for example, the male connectoris modified to include in the space between the center and outerconductor at one end a concavely tapered nonionizable relatively rigidinsulating material having an end recessed in the outer wall of theconnector portion. The sides of the tapered insulating material are ofthe form of a truncated cone and form a first angle with respect to theaxis of the center conductor. In this embodiment the female connectorportion, on the other hand, includes a protruding member of an elasticdeformable nonionizable insulating material anchored at the end of themale connector in the space between the center conductor and the outerconductor and which projects from the connector end beyond the outerconductor walls thereof. The protruding insulator has convexly taperedouter sides substantially in the geometry of a truncated cone. The sidesof the tapered portion forms a second or cone angle with respect to theaxis of said center conductor, and this angle is slightly smaller thanthe cone angle of the more rigid insulating member, previously cited. Incoupling the male and female connector portions together, the protrudingelastic insulator fits within the recessed rigid insulator.

The diameterof the front end portion of the elastic insulator is largeenough to abut a rearwardly located portion of the wall of the morerigid tapered insulator in the male connector when the two connectorportions are first pressed together in the union. COupling means,suitably a threaded collar, are provided on one of the connectorportions, which engages a threaded connector portion on the otherconnector portion for compressively joining together the two connectorportions. As the coupling collar rotates, the compression of the unionincreases and the deformable insulating material expands or bulges. Thisbulging commences at the point within the male connector where thedeformable projecting insulator first engages or abuts the tapered wallsof the more rigid insulator and thereafter, as greater and greatercompression is applied, continues and closes sequentially the gap inbetween the rigid insulator walls and the walls of the projectingelastic insulator from one end toward the other end. In high radiationfields or high voltage fields any path formed by an ionizable gaspresent between the center and outer conductors breaks down and causesleakage between the cited conductors. This bulging action sweeps out anyair initially present between the insulator portions of the male andfemale connectors and prevents the existence of a direct path of air orgas molecules between the center and outer conductors.

This invention was conceived or reduced to practice during theperformance of a contract with the US. Atomic Energy Commission.

3,514,741 Patented May 26, 1970 ICC This invention relates to lowleakage connectors, and more particularly, to electrical connectors foruse in environments of high ionization fields caused by atomic energy orhigh electrical voltages.

Heretofore it has not been possible to provide satisfactory electricalconnectors for use in high radiation fields. In high radiation fieldsgas molecules, such as air, are ionized into positive and negative ionswhich conduct electrical currents between separated electricalconductors at different electrical potentials. Such ionization createssevere difficulties in providing suitable detachable electricalconnections with; for example, neutron detectors used in makingmeasurements of high radiation fields of atomic energy. Conventionalconnectors contain a dielectric insulating material between the centerand concentric outer conductors. At the union where the male and femaleconnector ends join, an air passage is formed between the center andouter conductors. Unfortunately, in high radiation fields this airbreaks down or ionizes which results in electrical current flow orleakage between the center and outer conductors. In effect, this leakagecurrent shorts out, electrically, the remainder of the electricalcircuit and, hence, with atomic field measurements, the neutrondetector. This leakage phenomenon is also observed in connectors used inelectrical cables carrying high electrical Voltages in high altitudeapplications.

To avoid this problem in that application, electrical connectorsheretofore used were modified so as to permit the insertion of grease oroil in the union between the male and female connector portions. Thegrease or oil excluded air from between the outer and center conductorat the face of each connector portion. While this method is partiallysatisfactory, it possesses the obviously undesirable characteristic ofbeing very messy to use in the field.

Therefore, it is an object of this invention to provide an electricalconnector for use in high radiation fields;

It is another object of this invention to provide an electricalconnector which at the union does not contain an air passage between thecenter and outer conductors;

It is a further object of the invention to provide electrical connectingmeans in which the existence of an air path at the union and between thecenter and outer conductors is precluded without substantial use ofgrease or oils.

The foregoing and other objects and advantages of the invention,together with modifications thereof and equivalents thereto become moreapparent with an understanding of the following detailed description ofa preferred embodiment of the invention taken together with the figuresof the drawing in which:

FIG. 1 is an illustration in cross section of a novel electricalconnecting means embodying the invention; and

FIG. 2 is a graphical illustration of the sweeping action which occursto remove air and which is illustrative of the principles of theinvention.

Briefly stated, the invention encompasses a novel electrical coaxialconnecting means having male and female connector portions. Each of themale and female connector portions contains a center and an outerconcentrically surrounding cylindrical conductor separated and supportedfrom each other by dielectric material in the annular space between. Inaccordance with the principles of the invention, a protrudingsurrounding elastic deformable body of nonionizable insulative materialis anchored between the center and outer conductor of the femaleconnector portion and protrudes beyond the outer conductor or shell. Theouter sides of this protruding insulator are convexly tapered andcomprise the geometry of a truncated cone. The cone angle formed betweenthe walls thereof and the axis of the center conductor is a first angle.The male connector portion includes coaxially the center and outerconductors and an insulator therebetween. The insulator in thisconnector portion is a relatively rigid material and is recessed fromthe front or coupling end of the connector portion and concavely taperedfrom the front to the back so as to have the geometry of a truncatedcone, leaving the center conductor exposed and projecting. The coneangle formed by the walls of this nonresilient insulator portion and theaxis of the center conductor forms a second angle. However, this secondangle is slightly larger than the first angle formed by the protrudingtapered insulator of the female connector. The outer diameter of a tipof front end portion of the protruding tapered elastic insulator of thefemale connector is such as to engage and abut a recessed portion of thetapered more rigid insulator walls of the male connector when the twoare initially coupled together and the two insulators fit within oneanother.

Coupling means are provided for compressively uniting the male andfemale connector portions. In accordance with the principles of theinvention, as the coupling member is tightened to increase thecompression between the connector portions, the protruding elasticinsulator portion increasingly bulges radially from its front to itsback causing further and further portions of the walls of the protrudingelastic insulator to abut the tapered more rigid insulator wall portionsin the male connector portion Upon full compression, the protrudingconvexly tapered elastic insulator walls are in full contact with theconcavely tapered walls of the nonresilient insulating member of theother connector portion. In accordance with the principles of theinvention, the bulging proceeds from the front to the rear of theprotruding elastic insulator and a sweeping effect occurs between theinsulator walls which pushes out the air from the space previouslyexisting between the protruding tapered elastic insulator and the rigidrecessed tapered insulator. In accordance with another aspect of theinvention, the first and second angles are acute angles. Moreover, inaccordance with still further aspects of the invention, the protrudinginsulator is an elastomer, suitable silicon rubber; and the recessedinsulator is ceramic, suitably aluminum oxide.

FIG. 1 shows in partial cross section the male and female connectorportions forming the connector means or connector. Each of the twoportions are joined together in the figure to complete the electricaland mechanical union. The male connector includes a center conductor 1,conventionally of copper and an outer conductor or shell 2. The outerconductor is conventionally the shape of a hollow cylinder, consistingof a plated brass composition, which coaxially surrounds centerconductor 1. As is conventional, the male connector includes a threadedend portion 3 on the outer side of outer conductor 2, and a dielectricor insulating material 4 surrounds and supports center conductor 1within the concentrically surrounding outer conductor 2. Insulatingmaterial 4 is a rigid dielectric material, suitably the well knownceramic material, aluminum oxide. Insulator 4 is enclosed withinconductor 2 and is tapered concavely from the front end of the connectorto a back or recessed position to a distance behind the end of thecenter conductor 1. Thus, approximately a portion of center conductor 1protrudes from insulator 4. This portion of the insulating material thusdefines the geometry of a truncated cone. The tapered insulator wallsform an acute angle with the axis of center conductor 1.

It is noted that ceramic is a material which does not ionize in a fieldof high atomic radiation. The male connector portion includesconventional elements for clamping or soldering a coaxial cable at theright side of the illustration. Since such elements are old and wellknown, they are omitted from both the drawings and this description.

The female connector portion includes center conductor 6, suitablycopper, concentrically supported within a hollow outer conductor orshell 8, suitably plated brass. In between center conductor 6 and outerconductor 8 at the left side is an insulating material, insualtor 9 of adielectric material, suitably aluminum oxide. Insulator 9 in thisportion of the female connector is supported by a washer shapedconductor 7.

The left portion of the female connector in this embodiment, as isconventional, contains elements for permitting the connector to beelectrically connected with a coaxial cable. For purposes ofillustration such connection is illustrated in FIG. 1 by showing thewire braid portion 10 of a cable. For this purpose the elements includedin the shell includes a clamping member 12, only a portion of which isillustrated, which clamps wire braid 10 in electrical contact with theouter wall 8 of the female connector portion and mechanically holds suchcable in place. The clamping member is otherwise of conventionalconstruction and is not described further.

A treated ring collar or coupling member 14 is joined to the outer wallof the shell or outer conductor 8 by a split or snap ring washer 16which is seated in a groove in both outer conductor 8 and ring collar14. The treads 15 of the collar engage the treads on outer conductor 2of the male conductor.

Anchored within the space between center conductor 6 and the front endof outer conductor 8 is a convexly tapered insulator of any nonionizableelastic, deformable, compliant electrical insulating material, such asan elastomer and suitably silicon rubber which protrudes from the end ofouter conductor 8.

The front end portion of protruding insulator 18 has conically taperedouter sides or walls and is of the geometry of a truncated cone. In FIG.1 these sides engage and abut the tapered walls of rigid insulator 4 inthe male connector. Although not shown in this figure, when the male andfemale connectors are separated the taper of the sides of elasticinsulator 18 forms an acute angle with the axis of center conductor 9 or1, which angle is slightly smaller than the acute angle formed by thetapered walls of insulator 4 with the center conductors. However, asillustrated, when the two conductor portions are compressed together,elastic insulator 8 deforms to the same taper as that of the taperedwalls of the more rigid insulator 4. The outer diameter at the top endof elastic insulator 18 is the same as the inner diameter of the backrecessed portion of tapered insulator 4.

An annular void 20 exists between the top of seal 18 and the back of theopening in insulator 4. Another annular void 22 preferably is presentbetween seal 18 and outer conductor wall 2 in order to permit some typeof reservoir for air.

Additionally, it is desirable if the bottom edge of the female connectorinsulator 9 can be coated with grease to insure the prevention of anyair passage between conductor 8 and center conductor 6 at the back ofprotruding insulator 18. Moreover, the outer sides of insulator 18 maybe lightly coated with grease to insure positively that no air spacewill exist between its tapered walls and the tapered walls of the rigidinsulator 4.

It is noted that the diameter of insulator 18 at its tip or front end issubstantially the same as the diameter of the tapered walls of insulator4 at the back end of the conical cavity. This permits an initialengagement between insulator 18 and insulator 4 which fit within oneanother when the male and female connector halves are initially coupledtogether. It is further noted that the insulator material used is suchas to withstand the radiation fields to which it is exposed.

The construction of most parts of the male and female connectorillustrated in this embodiment are well known and conventional. Thus,the support and formation of the ring collar 14, the outer conductor 8,and the coupling therebetween with spinning nut 16 is conventional, asis the construction of clamping member 12, the formation and brazing inplace of insulator 9, and the cable connection to wire braid 10.Likewise, the construction of the metal cylinders forming the outer wall2 and the construction of center conductor 1 with insulating material -4between them is likewise conventional and is not further discussed. Theshape of insulator 4 in the male connector is obtained by forminginsulator 4 in a mold to the desired shape and taper before it isinserted, assembled, and brazed in place within hollow cylinder or outerconductor 2.

To construct the protruding insulator 18 a mold, not illustrated, ismounted to the female connector. Such mold is of the desired geometricalconfiguration. An extension is placed onto the center conductor 6 and afurther extension is connected therewith to duplicate the position ofmale connector center conductor 1. Liquid silicon rubber is then pouredinto the mold where it flows in between center conductor 6 and outerconductor 8, filling the entire annular space, including the anchoringgroove 15, to the desired heighth. The silicon rubber is then air curedand after the lapse of the necessary time for curing, the mold isremoved. This leaves the formed insulator remaining.

Reference is now made to FIG. 2 which more clearly illustrates theprinciples of the invention. FIG. 2 shows a portion of the centerconductors 1 and 6' and the protruding elastic 18' and rigid insulator4' during the several stages of compression undergone by the connectorelements upon fastening of the ring collar 14 in FIG. 1. The taper ofthe conical segment of insulator 18' is illustrated as an acute angle,a, while the taper of the rigid ceramic insulator 4' is shown as beingan acute angle, 5, that is slightly larger than a. Upon the initialcoupling between the male and female connectors, the two insulators fitwithin one another and the front edge or tip of the tapered wall ofinsulator 18' abuts the tapered wall of insulator 4 at the back end at apoint 24.

As the ring collar 14 of FIG. 1 is turned to tighten physically theconnection between the male and female connector, insulator 18 deformsor bulges and, hence, its outer sides assume in sequence the positionsof dotted lines 26, 28, 30 during successive stages of compression untilthe adjoining walls of both insulators are in full engagement. Since thedistance between the tapered sides of insulator 18' and 4' is smallestat the right side in the figure, the bulging initially causes partengagement 'between a further portion of the outer walls of insulator18' and insulator 4' at that end. With increased engagement illustratedat 28 and 30 occurring with successive increases of coupling pressure.Thus, as is apparent from the illustration, the manner in which thetapered insulator sides engage sequentially causes a sweeping actionfrom right to left in the figure; and, thus, sweeps out any airinitially present between the outer side of insulator 1-8 and innerwalls of insulator 4'.

Reference is again made to FIG. 1. Since a path of air between outerconductor 2 and the center conductor 1 has been excluded, fields of highradiation cannot cause electrical leakage in the connector. Theinsulators withstand and do not break down during exposure to the atomicradiation. Accordingly, the novel connector of the inventionsatisfactorily provides a portable connection useful in high radiationor electrical fields.

The elastomer, silicon rubber, used in the preferred embodiment of theinvention, has several additional properties useful in the connectorcombination. One, the silicon rubber tends to cold flow; that is, itexpands to fill any slight voids that may be present, while it stillretains the ability to restore itself to its original shape. Secondly,the surface of silicon rubber tends to cling to other surfaces. In theconnector of the invention, the silicon rubber thus clings to theceramic insulator resulting in a firm seal between the two. 7

Additionally, it is noted that aluminum oxide is used as thenonionizable insulator of one of the connector portions. In low atomicradiation fields and in high altitude electrical applications, amaterial such as Teflon may be substituted for ceramic insulator 4.While Teflon decomposes in fields of high atomic intensity it is bothuseful and preferable in more conventional high altitude electricalapplications and fields of lower intensity atomic radiation.

It is understood that the foregoing description of an embodiment of theinvention has been presented herein to clearly illustrate the invention,and is not intended in any way to limit the invention since numerousother equivalents which do not depart from the spirit and scope of thedisclosed invention suggest themselves to those skilled in the art,

For example, the relative location of insulator 18 and insulator 4 maybe interchanged between the male and female connectors. Likewise inaccordance with the principles of the invention, the shape of theelastic member 18 may be made that of the rigid or nonelastic insulator4, and vice versa. In addition, the details of the conventional couplingmeans can be changed so long as they incorporate the relationship setforth herein between the elastic deformable seal 18 and a rigid ornondeformable insulator 4 in the other half of the connection meansmaintaining the same geometrical relationship so as to effectively causethe air to be swept out of the space between the tapered sides of eachmember as the male and female connector portions are being fullycompressed in engagement.

Accordingly, it is to be expressly understood that the invention is tobe broadly construed.

What is claimed is:

1. Electrical connector means for use in high radiation fieldscomprising: a male connector and a female connector, each of whichincludes an elongated center conductor and a coaxial outer conductorsurrounding said center conductor; said male connector including arelatively rigid substantially nonionizable insulator between itsrespective center and outer conductors; said rigid insulator beingtapered concavely from a front end portion of its respective outerconductor and internal thereof and forming a first angle with respect tothe axis of said center conductor; said female connector including aprojecting tapered insulator of elastic substantially nonionizablematerial surrounding the respective center conductor and anchored inplace between the respective center and outer conductors; saidprojecting insulator comprising a convexly tapered projecting portionwhich extends beyond its respective outer conductor and is adapted tofit within said rigid insulator and having a taper which forms a secondangle With respect to the axis of said center conductor; said secondangle being slightly smaller than said first angle; and, wherein a frontend portion of said projecting insulator is of the same outer dimensionas the inner dimension of a rearwardly located recessed portion adjacentan end of said concave taper in said rigid insulator for causing initialengagement between said insulators upon coupling and for leaving a spacebetween an end of said convexly tapered projecting portion and saidrigid insulator as a reservoir for air; and, coupling means for couplingtogether compressively said male and female connectors; where-by withthe application of consecutive increases of coupling pressure saidelastic insulator increasingly bulges radially and abuts consecutivelyfrom one end to the other the walls of said rigid insulator and any airor gas initially existing in the space between said respectiveinsulators is swept out by the sequential mating action.

2. The invention as defined in claim 1 wherein said convexly taperedprojecting insulator comprises the geometry of a truncated cone; and,wherein said concavely tapered rigid insulator comprises the geometry ofa truncated cone.

3. The invention as defined in claim 2 wherein said tapered protrudinginsulator protrudes beyond both the inner and outer conductors of saidfemale connector; and,

7 wherein said tapered rigid insulator leaves exposed a portion of saidrespective center conductor.

4. Electrical connector means for use in high radiation fieldscomprising: a male connector portion and a female connector portion,each of which comprises an elongated center conductor and a coaxialouter conductor surrounding said center conductor; said male connectorportion including a relatively rigid substantially nonionizableinsulator between the outer and center conductors tapered concavely fromthe face end and having the geometry of a truncated cone, said insulatorportion having a taper which forms a first angle with the axis of saidcenter conductor; said female connector portion including a projectingtapered insulator of elastic substantially nonionizable materialsurrounding the respective center conductor and anchored in placebetween its respective center and outer conductors, said projectinginsulator comprising a convexly tapered projecting portion having thegeometry of a truncated cone which fits within said rigid insulator andhas a taper which forms a second angle with the axis of said centerconductor; said second angle being slightly less than said first angle;and wherein a front end portion of said projecting insulator is of thesame outer dimension as the inner dimension of a rearwardly locatedrecessed portion adjacent an end of said concave taper in said rigidinsulator for causing initial engagement between said insulator whileleaving a space between an end of said convexly tapered projectinginsulator and said rigid insulator as a reservoir for air; and, couplingmeans for coupling together, compressively, said male and femaleconnector portions; whereby with the application of consecutiveincreases of coupling pressure said elastic insulator increasinglybulges radially and abuts consecutively, from one end to the other, thewalls of said rigid insulator and air or gas initially existing in thespace between the respective insulators is swept out.

References Cited UNITED STATES PATENTS 2,088,949 8/1937 Fekete.2,379,942 7/1945 Webber. 2,892,990 6/1959 Werndl. 3,292,117 12/1966Bryant et a1. 33397 3,297,975 1/1967 Pope 339-60 3,328,744 6/1967 Fiske33961 RICHARD E. MOORE, Primary Examiner I. H. McGLYNN, AssistantExaminer US. Cl. X.R. 339l77, 278

